This invention relates to hardware for connecting wooden members in rigid relation in general, and in particular to an A-frame bracket for securing A-frame members to an overhead beam in playground equipment.
Play structures for the entertainment and exercise of children have long been in use. Particularly popular with children has been the swing set which consists of an overhead beam supported on opposite ends by frame members with chairs or seats suspended from the overhead member on chains or ropes. Swing sets or other play structures may be constructed of metal or plastic, but metal is costly and prone to rust, and plastic tends to lack the necessary strength to stand up to heavy use by children. Swing sets may also be constructed from modern weather-resistant treated timber which is strong and durable and does not require painting. Wooden sets present a rugged and attractive appearance and are not subject to rusting.
Because of the bulk and weight of assembled play structures they are rarely shipped from the manufacturer in assembled form, but are often sold as kits for home assembly by the consumer. Because the swing set features the intersection of a number of angled beams, fabrication of swing sets from standard timber lengths without specialized hardware has been restricted to professional carpenters and skilled hobbyists. A play set must be rigidly braced and the structure must be capable of withstanding forces and loads in addition to those due to the swinging motions of the suspended seats.
All-wood playsets have long been known to the art, but wood joinery requires advanced carpentry skill. Previous hardware kits for constructing wooden play sets are also known.
For example, U.S. Pat. No. 4,966,309 to Baer discloses a swing assembly hardware kit. The kit includes 4 brackets for joining together the A-frame to the overhead beam at each end of the swing. The use of multiple brackets in joining the A-frame to the overhead beam leads to several disadvantages. First, the placement of the brackets becomes critical because each bracket must align with the other brackets. In addition, a multi-bracket system lacks the necessary integrity to properly secure the A-frame to the overhead beam. Moreover, as forces are exerted upon the swing set, the connection may loosen due to the multi bracket set-up.
Another example of a bracket system used to join an A-frame to an overhead beam for a swing set can be found in U.S. Pat. No. 5,364,312 to Cunard et al. Cunard discloses a two piece bracket system. The first bracket is a trapezoidal stamped metal plate with side flanges and an outwardly extending top flange. The second bracket is an elongated stamped metal part with an inverted U-shaped cross section formed from a top rectangular surface and two generally triangular side walls (webbing). The bracketing system disclosed in Cunard suffers from the same disadvantages as the bracketing system disclosed in Baer. For example, because the A-frame bracket is formed from two separate pieces, it lacks the stability provided by a one piece system. In using the Cunard bracket, each A-frame member is only secured to a flat flange on the second bracket with the trapezoidal bracket mounted opposite the second bracket, as shown in FIG. 5 of the Cunard patent. However, in this configuration there is no direct connectivity between the two separate brackets thereby resulting in an inferior weak joint in comparison to the one piece bracket design of the present invention. Thus, as the swing set is used over time the brackets forming the joint may become loose from the forces exerted upon the play set by the user. Furthermore, a two piece system also is more difficult to install because the brackets must be properly aligned to gain maximum stability. Finally, the Cunard design provides screw holes that align close to the edges of the members. This configuration may cause the wood members to split or splinter either during installation or during actual use of the play set resulting in a weak unstable connection.
Thus, what is needed is a one piece A-frame bracket that provides maximum stability, has no welded joints, is made from heavy gauge metal and is user friendly.